Chemical metallizing process



United States Patent 3,438,805 CHEMICAL METALLIZING PROCESS Earl M.Potrafke, New Castle County, De]., assignor to E. I. du Pont de Nemoursand Company, Wilmington, Del., a corporation of Delaware No Drawing.Filed Apr. 6, 1966, Ser. No. 540,517

Int. Cl. B44d 1/22 US. Cl. 117130 16 Claims This invention relates to achemical metallizing process and more particularly to a method ofchemically metallizing a substrate by heating a metal salt/phosphinecomplex in the presence of the substrate.

Metal-coated articles are presently enjoying wide utility. They areoften conveniently obtained by chemical or non-electrolytic methods,starting with a compound of the coating metal and converting it to themetal under controlled conditions. In general, however, the knownmethods are not entirely satisfactory; they each have one or moredisadvantages such as requiring exceedingly high temperatures orpreformed organometallic compounds, or are limited to aqueous platingbaths or to the use of active metal substrates in accordance with theelectro motive series, or are otherwise not readily adapted to plating awide variety of substrates. Of particular interest at the present timeis the coating of non-metallic substrates such as plastics.

It is an object of this invention to provide a new chemical platingmethod utilizing readily available metal salts. Another object is toprovide such a method which is not dependent on aqueous plating baths,or the activity of the metal substrate in accordance with theelectromotive series. Still another object is to provide such a platingprocess for metallizing a wide variety of substrates, includingnon-metal as well as metal substrates. These and other objects willbecome apparent from the following description of the invention.

It has now been discovered that a wide variety of substrates can bechemically metallized by the process which comprises heating a metalsalt/phosphine complex derived from one mole of a non-organometallicsalt of a normally solid heavy metal of the Deming Periodic Table andabout 1 to 4 moles of a triorgano phosphine in which each organo groupis a hydrocarbyl or dihydrocarbylamino radical in the presence of thesubstrate to be metallized at a temperature of about 25 to 350 C., butbelow decomposition temperature of the substrate and the heavy metalsalt alone, provided that when the substrate is not a heavy metal of theDeming Periodic Table other than the plating metal, the metalsalt/phosphine complex is in substantially pure form in direct contactwith the substrate. By metallized is meant metal-coated ormetalimpregnated. By normally solid heavy metals is meant heavymetalswhich are solid at normal ambient temperatures, thereby excluding metalssuch as Hg and Ga which are liquid at temperatures as low as about 30 C.By plating metal is meant the heavy metal of the salt from which thecomplex is derived. By substantially pure form is meant undiluted by anysubstantial amount of solvent, diluent or carrier. Minor amounts ofimpurities and additives are readily tolerated.

When the substrate is a normally solid heavy metal of the DemingPeriodic Table other than the plating metal, the substrate may beimmersed in a bath containing the metal salt/phosphine complex dissolvedin an inert solvent and the bath is heated for a time sufiicient toprovide an adherent coating of the plating metal on the substrate.

When the substrate is not a heavy metal of the Deming Periodic Tableother than the plating metal, the metal salt/phosphine complex is heatedin substantially pure form in direct contact with the substrate. Whendirect contact between the complex in substantially pure form and thesubstrate is required, it is most conveniently provided by coating thesubstrate with the complex alone, especially in the case of a liquidcomplex, or by mixing the complex with a volatile carrier such as asolvent or diluent, coating the substrate with the mixture, evaporatingthe volatile carrier and heating the coated substrate therebymetallizing the substrate.

Because the metal salt-phosphine complexes are soluble in a wide varietyof solvents, metal impregnates as well as coatings can be produced witha wide variety of polymeric substrates that are also soluble in suchsolvents and can be recovered and reconstituted by solvent evaporation.For impregnating a substrate such as plastic the metal salt/phosphinecomplex and a soluble polymer are dissolved in a mutual inert volatilesolvent, the solvent is evaporated to form an intimate metalsalt/phosphinepolymer mixture which is heated to produce the impregnatedplastic. A solvent is chosen which softens, swells or dissolves theplastic substrate thereby allowing the plating components to penetratethe surface or to become completely and intimately associated therewith.Solutions of the metal salt/phosphine complex and the substrate polymercan be cast as films, spun into fibers or molded into any desired shapeand, with evaporation of the solvent and heating, converted into ametallized product.

Broadly, the method of this invention comprises heating the metalsalt/phosphine complex in the presence of the substrate to be metallizedat the temperature required to etfect the metal salt/phosphine to metaltransformation in the particular case. The required temperature, whichmay be as high as 350 C., but usually is in the range of 25 to 250 C.,is significantly lower than that required to decompose the metal saltalone to the free metal.

When the substrate is a normally solid heavy metal of the DemingPeriodic Table other than the plating metal, plating temperaturesgenerally range from about 25 to 150 C. When the substrate is other thanthe specified heavy metals, somewhat higher temperatures in the range ofabout to 250 C. are generally required. In other words, metal platingwith the same metal salt/ phosphine complex may require diiferenttemperatures depending upon whether or not the substrate is one of thespecified heavy metals.

While the exact nature of this phenomenon is not definitely known, it isbelieved that the specified heavy metals may enter into an exchangereaction with the heavy metal of the complex. Although it is notintended that this invention be limited to any particular theory, theseexchange reactions could account for the lower temperatures encounteredwith heavy metal substrates.

However, these exchange reactions do not follow the normal relationshipsencountered in the electromotive series of the metals as shown forexample by Lange in Handbook of Chemistry, 10th Edition, page 1218, Me-Graw-Hill Book Co. In accordance with this invention, metals such asaluminum, manganese, zinc, chromium, ir-on, cobalt, nickel and tin arereadily plated on a substrate such as copper, which is lower down in theelectromotive series than these plating metals. Such exchange reactionsare contrary to the accepted rules of the electromotive series.

It is possible that the presence of the phosphine in the complex mayalter the normal forces in the electromotive series. It has been foundthat by proper selection of the phosphine and solvent, any of the heavymetals can be plated on any other heavy metal at substantially reducedtemperatures.

The complexes used in accordance with this invention are derived in partfrom salts of the normally solid heavy metals of the Deming PeriodicTable. These heavy metals are defined in the Deming Periodic Table asshown by H. G. Deming in Fundamental Chemistry, 2nd edition (1947), page255, John Wiley & Sons, Inc. and by Lange in Handbook of Chemistry, 10thEdition, pages 56 and 57. Suitable heavy metals which may be used inaccordance with this invention include: Cu, Ag and Au (Group I-B); Znand Cd (Group II-B); Al, T1 and In (Group III); Sn, Pb, Ti and Zr (GroupIV); Sb, V, Nb, Ta and Bi (Group V); Cr, Mo and W (Group VI); Mn and Re(Group VII); Fe, Ru, Co, Rh, Ni, Pd, Pt, Os and Ir (Group VIII).

The heavy metal salts from which the metal salt/ phosphine complexes arederived are non-organometallic salts. By non-organometallic salt ismeant a salt which is free of carbon-metal bonds. In other words, thisinvention is directed to the utilization of heavy metal compounds intheir commonly available essentially organic salt forms and does notrequire that the metal salts first be activated by conversion to anintermediary organometallic form. The heavy metals are commonlyavailable and conveniently used as the chlorides, bromides, iodides,cyanides, nitrites, nitrates, perchlorates, fluoroborates, carbonates orcarboxylates such as acetates and trifiuoroacetates.

Preferred plating metals are the ductile, noble and precious metals ofGroups LB, and VIII, especially the salts of silver, copper, gold,nickel, cobalt, palladium and platinum. Still other preferred platingmetals are titanium, chromium, zinc and tin. These are preferablyemployed as the readily available chlorides, bromides and iodides, butsometimes, as in the case of silver, are more advantageously used as thenitrites, nitrates or perchlorates.

The complexes are also derived in part from triorgano phospines in whicheach organo group is a hydrocarbyl or dihydrocarbylamino radical. Eachof the hydrocarbyl groups, including those in the dihydrocarbylaminoradical, may he aliphatic, cycloaliphatic or aromatic and, for reasonsof availability and economy, normally contain from about 1 to 10 carbonatoms, but may contain up to about 18 carbon atoms. These groups may bestraightchain, branched-chain, saturated or unsaturated includingethylenic and acetylenic unsaturation. Exemplifying such groups aremethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, amyl, hexyl, octyl, decyl, dodecyl, hexadecyl, octadecyl,propenyl, allyl, butenyl, propargyl, octadecenyl, cyclopentyl,cyclohexyl, cyclohexenyl, phenyl, tolyl, xylyl, ethylphenyl, styryl anddodecylphenyl. The trialkyl phosphines are preferred, particularly thetrilower alkyl phosphines having from about 1 to carbon atoms in eachalkyl group.

The hydrocarbyl secondary amino groups are preferably, for reasons ofavailability and economy, di-lower alkylamino groups where each alkylhas from about 1 to 5 carbon atoms such as dimethylamino, diethylamino,methylethylamino, dibutylamino, methyl amylamino and diamylamino.Suitable homologs and analogs include dioctylamino, methyloctadecylamino, ethyloctadecenylamino, methyl cyclopentylamino, methylcyclohexylamino, octyl cyclohexylamino, dicyclohexylamino, N-methylanilino, N-ethylanilino and N-methyl toluidino. The hydrocarbylgroup may also constitute a single divalent radical such as thepyrrolidino and piperidino radicals.

The process of this invention may be carried out using a preformed metalsalt/phosphine complex, or the complex may be prepared in situ by addingthe metal salt and phosphine separately to a solvent in which thecomplex is soluble. In either case, the complex is formed and acts as anecessary component in the process. When the complex is formed in situsmall excesses of metal salt or phosphine may be present. These do notinterfere with the metallization process.

As is Well known in the art, phosphines and heavy metal salts generallyform definite coordination complexes involving from 1 to 4 moles of thephosphine per mole of the salt. For etiicient utilization of the heavymetal salt in forming the complex in situ, the phosphine is normallypresent in amounts corresponding to at least about one mole per mole ofheavy metal salt. More than about four moles of the phosphine per moleof salt is generally not needed, but may be used, if desired. Theoptimum amount of the phosphine may vary depending on the particularheavy metal salt and the substrate to be coated. Usually, however, onlyabout two moles of the phosphine are needed per mole of salt andsometimes only about one, particularly in the case of Group I-B metals.The formation of definite metal salt/phosphine complexes constitutes animportant practical advantage since the complexes are easily obtainedpure and can be conveniently stored and handled at ordinarytemperatures.

In general the metal salt/phosphine complexes decompose to form metal ator slightly above their melting points and in general this is completedat temperatures below about 350 C. As a class, the triaryl phosphinecomplexes are thermally more stable than the trialkyl phosphinecomplexes and require higher metallization temperatures. This may beadvantageously used where enhanced thermal stability of a complex isneeded as in controlled and step-Wise metal deposition. Thus, the widevariety of phosphines that are available enables one to control or varythe temperature of metallization to suit the particular processing need.

The metal salt/phosphine complexes, in contrast to the metal salts fromwhich they are derived, are highly soluble in a wide variety of organicsolvents making possible the formulation of a wide range of platingcompositions. The solvent of course should be substantially inert to theplating ingredients and the substrate. Suitable solvents includealcohols such as methanol, ethanol, 2- propanol and 2-methyl-1-propanol;ethers such as diethyl ether, furan, tetrahydrofuran and dioxane;ketones such as acetone and methyl ethyl ketone; hydrocarbons such aspentane, hexane, isooctane, tetradecane, benzene, xylene and toluene;halogenated hydrocarbons such as chloroform, methylene chloride, carbontetrachloride, chlorobenzene, dichlorobenzene, trichloroethylene, 1,1,2,2 tetrachloro-1,2-difiuoroethane, l,1,2-trichloro-1,2,2-trifluoroethane, trichlorofluoromethane, chlorotrifiuoromethane andmixtures and azeotropes thereof; nitriles such as acetonitrile,butyronitrile and benzonitrile; amines such as triethylamine,tributylamine, pyridine and picoline; amides such as dimethylformamide,dimethylacetamide, hexamethylphosphoramide and hexaethylphosphoramide;and esters such as ethyl acetate, butyl acetate and amyl acetate.

The main function of the solvent is to provide liquid, easily handledcompositions which can effectively bring the metal salt/phosphinecomplex in intimate contact with the substrate to be metallized. Thesolvent may also serve to transfer heat to the metallizing componentsand as a vehicle for other ingredients having beneficial effects such asplating promoters and surface conditioners. Volatile solvents arepreferred, particularly those which can be evaporated from themetallizing compositions at temperatures at or below the temperature atwhich metallization occurs.

The method of this invention can be applied to a wide variety ofsubstrates, including metallic and non-metallic materials. The metalsmay be any of those normally used for decorative, structural orelectrical purposes. These are usually the normally solid heavy metalsof the Deming Periodic Table and alloys thereof. For practical reasonsthe substrate metal is generally different from the plating metal exceptwhere special elfects such as relief are desired. Besides the heavymetals, other metals may also serve as substrates including the rareearths such as cerium and actinides such as uranium. As pointed outabove the substrate metal may be higher or lower than the plating metalin the electromotive series of the metals.

There may also be used as substrates siliceous solids such as glass,Pyrex glass, spun glass, and asbestos; carbonaceous materials such asgraphite and the various amorphous carbon blacks; refractory materialssuch as Carborundum, ceramics and cermets; natural and syntheticcellulosic materials such as cotton, hemp, jute, paper, parchment, wood,cellulose acetate, and rayon; proteinous materials such as silk, wool,leather, mohair and fur. Still other important substrates are thesynthetic polymeric compositions exemplified by the polyvinyls such aspolyacrylonitrile, polyvinyl chloride, polytrifiuorochloroethylene,polytetrafiuoroethylene, polystyrene, polyethylene, polypropylene,polyvinyl acetate, polyvinylidene fiuoride, poly(alkyl methacrylates)and copolymers thereof; polybutadiene, poly(diallyl esters) such aspoly(diallyl phthalate); polyamides such as nylon, polyimides,polyesters, polyurethanes, polyacetals, melamine-formaldehyde,urea-formaldehyde, phenol-formaldehyde and epoxies. When the substrateis a polymeric material, the metallization temperature should be belowthe deformation temperature of the polymer.

The substrate may be particulate, for example powdered, or it may have acontinuous surface in the form of a sheet, film, tape, foil, wire,fiber, fabric or foam. It may be a highly surface porous mass which isto be impregnated and coated at the same time such as a porous catalystsupport.

As is well known in the plating art, for best results the substrate tobe plated should be clean especially with respect to grease and loosescale. Any of the known techniques may be used to prepare the surface tobe plated. For example, metal surfaces can be treated as described byBurns and Bradley in Protective Coatings for Metals, 2nd Edition,Chapter 2, Reinhold Publishing Corporation. Plastic surfaces can also bepreconditioned according to known techniques. For example, the surfacecan be mechanically satinized as described by Bruner and Baranano inModern Plastics, December 1961, and in Chemical and Engineering News,Mar, 25, 1963, pages 48 and 49. Or the surfaces may be chemicallyetched, as in the case of polyfluoroethylene being treated with analkali metal-amine solution as described in Canadian Patent No. 653,304,or with an alkali metal-aromatic ether solution as described in US.Patent No. 2,809,130.

It is often beneficial to condition the surfaces to be plated,especially metal surfaces, with conditioners such as the commonlyemployed hydrohalic acids including hydrochloric, hydrobromic,hydrofluoric and hydroiodic acids or sulfuric acid, or by treating witha small amount of an inorganic reducing salt such as stannous chloride.Such promoters may be incorporated directly into the metalsalt/phosphine plating composition of this invention, if desired.Conveniently this may be done in a carrier solvent, especially alcoholssuch as methyl, ethyl and propyl alcohols.

As an improvement Within the scope of this invention, it has beendiscovered by other inventors that for many of the metal salt/phosphinecomplexes, especially those derived from the noble metals, thetemperature or time required for metallization in accordance with thisinvention can be further reduced by sensitizing the metal salt/phosphine complex to subsequent thermal treatment. Sensitization may beaccomplished by incorporating into the metal salt/phosphine complexplating composition a thermally dissociable free radical generator suchas carbon tetrabromide or an organic peroxide, or by irradiating thecomplex with ultraviolet light, or exposing it to an electron beam orcontacting it with a spark discharge. By these techniques thetemperature requirement can be reduced by as much as 100 C, for platingon nonmetallic substrates. The sensitizing step is particularlyadvantageous in the case of heat sensitive substrates such as certainplastics. This improvement allows the use of a wider variety ofcomplexes with these substrates.

The following examples, illustrating the novel method disclosed hereinfor metallizing a wide variety of substrates, are given without anyintention that the invention be limited thereto. In these examples, allparts and percentages are by weight unless otherwise specified;solutions of metal salt/phosphine complexes, where employed, wereprepared and used in non-metallic (usually glass) containers; and metalsto be plated were in the form of 1 in. x 1 in. x A; in. coupons unlessotherwise noted. Preformed metal salt/phosphine complexes, where used,were prepared by known methods. Adherence of the metal coatings to thesubstrate was measured by the Scotch tape cross-hatch test.

(A) GROUP I-B PLATING Examples 1 to 15 A gold plating stock solution wasprepared by dissolving 1 part of (CH P-AuCl in parts of ethanolcontaining 5 parts of added concentrated hydrochloric acid. Aliquotswere used to plate immersed test coupons of various metals by heating at80 C. for the time indicated in the table below.

TABLE I Substrate Example Time, hours Thallium- Tin 14 Tungsten Afterthe plating treatment, the coupons were removed, washed with water, thenacetone, and inspected. All had an adherent gold coating.

Examples 16 to 25 The procedure of Examples 1-15 was repeated with asolution containing 1 part of (CH P-AuCl, 200 parts of methanol and 3parts of concentrated hydrochloric acid to produce adherent gold plateson various metal substrates at 60 C. and the time indicated in the tablebelow.

TABLE II Substrate Example Time, hours 405 stainless steel 24. 410stainless steel. 25 430 stainless steel Example 26 Example 27 Theprocedure of Example 26 was repeated using 200 mesh powdered nickel asthe substrate 'with the same result.

Example 28 The procedure of Example 26 was repeated using 200 meshpowdered stainless steel as the substrate with the same result.

Example 29 A plating solution containing 1 part of (CH P-AuCl, 200 partsof ethanol and 3 parts of concentrated hydrochloric acid was prepared. A316 stainless steel coupon was placed in the solution for 2 hours atboiling. An adherent gold coating was produced on the 316 stainlesssteel.

Example 30 The procedure of Example 29 was repeated except that 200parts of 2-propanol were substituted for the ethanol with the sameresult.

Example 31 The procedure of Example 29 was repeated except that 200parts of 2-methyl1-propanol were substituted for the ethanol with thesame result.

Example 32 The procedure of Example 29 was repeated except that 200parts of acetone were substituted for the ethanol with the same result.

Example 33 The procedure of Example 29 was repeated except that 200parts of chloroform were substituted for the ethanol with the sameresult.

Examples 34 to 41 Using the procedure of Examples 1 to 15, variousgold-plating compositions were used to adherently plate various metallicsubstrates under the conditions indicated in the table below.

TABLE III Exam- Plating Solution, parts Temp., Time, Substrate ple 0.hrs.

34 1 pt. (CH3)3P-A11Cl, 80 pts. 80 1 Bronze.

95% ethanol, 3 pts. cone. HBr.

35 1 pt. (C4HD)PA11CI, 250 pts. 80 6 Copper.

acetonitrile.

36. 1 pt. (CaHmP-AuCl, 100 pts. 100 0.1 Mild steel.

dirncthylformamidc, 20 pts. acetic acid.

37 1 pt. (GHmP'AuI, 160 pts. 60 0. Niobium.

methanol, 1 pt. conc. HF.

38 1 pt. (CHmRAuI, 160 pts. 60 1 Aluminum.

methanol, 1 pt. conc. HF.

39 1 pt. (CHa)aP-Au1, 160 pts. 60 1. 5 Uranium.

methanol, 1 pt. eonc. HF.

40 1 pt. (CHahP-AuI, 160 ts. 50 1.5 Aluminum.

acetone, 1 pt. cone. H

41 1 pt. (CeH5)3P-AIII, 250 pts. 80 Stainless 95 0 ethanol. steel.

Example 42 Silver-plating compositions, prepared by dissolving 1 part of(CH P-AgI in 250 parts of 2-propanol, and adding 0.5 part ofconcentrated hydrochloric acid, produced lustrous, adherent silverplates on brass coupons immersed in the boiling solution for 0.5 hour.

Example 43 The procedure of Example 42 was repeated using 250 parts oftriethylamine in place of the 2-propanol with the same result.

Example 44 The procedure of Example 42 was repeated using 250 parts ofacetone in place of the 2-propanol with the same result.

Example 45 The procedure of Example 42 was repeated using 25 0 parts ofacetonitrile in place of the 2-propanol with the same result.

Examples 46 to 51 Various silver-plating compositions were used in theprocedure of Examples 1 to 15 to produce lustrous adherent silver plateson various substrates under the conditions indicated in the table below.

TABLE IV Exam- Plating Composition, parts Temp., Time, Substrate ple 0.hrs.

46 1 pt. (CH3) P-AgI, 20 pts. 50 2. 5 Phosphor acetone. bronze. 47 1 pt.(CH P-AgI, 16 pts. 50 3 Copper (200 acetone. mesh) powder. 48 1 pt.[(CeHmPh-AgNo 1 Everdur" 16 pts. methanol. Cnu-Si-Mn a 0y. 49 1 pt.[(CBH5)2CH3P]4-ANO3, 80 0.2 Copper.

40 pts. acetonitrile. 50 1 pt. (CHmP-AgNOz, 40 pts. 80 0. 2 Do.

acetonitrile. 51 1 pt. (CoHrOaP-AgNOz, 80 O. 2 D0.

pts. acetonitrile.

Examples 52 to 55 Various copper salt/phosphine complexes were used inthe procedure of Examples 1 to 15 to produce lustrous, adherent copperplates on various substrates under the conditions indicated in the tablebelow.

TABLE V Exam- Plating Solution, parts Temp., Time, Substrate ple 0. hrs.

52 1 pt. [(CeH5)3P]2-C11Clz, 100 0.3 Mild steel.

100 pts. dimethylionnamide, 20 pts. acetic acid. 53 1 pt.[(CiHt)sP]z-CuC1z, 60 2 Cast iron.

30 pts. methanol, 0.05 pt. cone. HCl. 54 1 pt. [(C4H P]z'Cl1Clz, 80 2Brass.

100 pts. 95% ethanol, 5 pts. cone. H01. 55 1 pt. (C4Hn)aP-CI1OC(O)CH 803 Gold.

100 pts. acetonitrile.

Example 5 6 The liquid complex, (C H PAu'Cl, was spread on a siliconwafer which was then heated on a 180 C. hot plate. Within 5 minutes, theWafer had become coated with an adherent, electrically conductive goldlayer. When cooled, the resistance of the wafer was less than 0.5ohm/cm. or less than of the original resistance.

It will be apparent to those skilled in the solid state electronics artthat this process and the gold-coated silicon produced thereby areuseful for preparing integrated microcircuits.

Example 57 A 0.1% solution of (CH P-AgNO in acetone was spread over a 1in. x 1 in. film of polytetrafluoroethyleue whose surface previously hadbeen treated with a sodiumnaphthalene-te'trahydrofuran solutionessentially as disclosed in US. Patent No. 2,809,120. After the acetonehad evaporated, the film was placed with the coated side up on a 100 C.hot plate while the coated side was simultaneously heated with a hot airstream from a commercial hair dryer at a somewhat lower temperature. Abright silver coating appeared almost immediately. The silver coatingwas flexible, adherent, had a resistance of about 10 ohm/cmfi, and couldbe wiped with a paper towel to a mirror bright finish. Rubbing andcompressing the coating with a spatula further improved its luster andconductivity.

Example 5 8 Example 57 was repeated on a film of Delrin polyacetal resinthat had previously been satinized as described by Bruner and Barananoin Modern Plastics, December 1961. Simply heating on a hot plate at C.for 15 minutes produced a lustrous, flexible, adherent andelectrically-conductive silver coating on the film.

9 Example 59 The procedure of Example 58 was repeated except that anuntreated Zytel polyamide resin film was used as the substrate withessentially the same result.

1 (C) PLATING WITH GROUP III METALS Example 70 Aluminum was plated oncopper by heating a copper test coupon at 35 C. for 6 hours in a platingsolution Example 60 prepared by adding 20 g. of triphenylphosphine(0.076 The procedure of Example 58 was repeated except that mole) in 100ml. of ether to a filtered solution containing 5 g. of anhydrous -AlCl(0.038 mole) in 100 ml. of ether an untreated Mylar polyester film wasused as the sub d Strata with essfinfiany the same result an removingthe small amount of 011 that separated.

Example The procedure of Example 5 8 was repeated except that Thanipmwas plated on 9 by heating a copper test an untreated Kapton type Hpolyimide film was used as coupon m a solution contanilng T1OC(O)CH3 thesubstrate with essentially the same result (0'01 11.1016) andof.tr.lbutylphosphme (0'02 mole) mole) in 50 m1. of acetonitrile for 3hours at 80 C. Example 62 Example 72 A solution containing 1 part of (CHC*H P-AgNO 1 part of a film-forming vinylidene fluoride/tetrafluoro-Infimm Was heavlly ileposlted a g l coupon y ethylene copolymer and 4parts of acetone was cast as a heating the gold coupon 1n a solut1o nconta1n1ng 2.2 g. of film on aluminum foil. The acetone was evaporatedand 20 Incls H1016) and f trlb ylph phu le (0.04 the coated piece heatedat 180 C. for 5 minutes to demole) 111 50 1111- f aC t mtnle for 3 hoursat 80 C. glellltgraufieitglle, silvery coating WhlCh was adherent to the(D) PLATING WITH GROUP IV METALS Example 63 Example 73 The Procedure ofExamplfi 62 was repeated except h A lustrous and adherent tin coatingwas obtained on a glass plate was used in place of the aluminum foilwith copper by heating a copper test coupon for 2 hours at the sameresult. The metal-impregnated coating adhered 0 in a plating SolutionPrepared by mixing 1 part to the glass. each of SnCl -2H O and (C H P inabout 10 parts of Example 64 methanol. The emission spectrum of thecoating corre- A piece of Torvex ceramic honeycomb (4 in. in dispondedto that Of metalliC t nameter, l in. thick and having a in. pore size)was Exam 1e 74 dipped into one liter of a 1% solution of (CH P-Ag N O Pin acetonitrrle, air dried to evaporate the acetonitnle, The procedureof Example was repeated 6Xcept that 2 i g l f gtgl zg gf if) gvgl gg ggilz 6 ggti r l g a silver telst coupon was used 1n place of copper withthe a PTOXlm same resu t. The procedure was repeated eight times tobuild up a Examples 75 to 81 continuous silver coating throughout theporous structure Metal plates were obtained by immersing a substrate inSuch product, presenting a large silver surface, but with 40 a pl ti p st on and heating for 1-6 hours under the its open honeycomb structuresubstantially unchanged so C0I1d1t10 I1 S Summarlled 1n the p belOW- TPlating that gas flowing through it remains substantiallyunimcomposltlons w P p v approxlmatqly peded, is useful as a silvercatalyst in vapor phase reacmolar P P Of a P P e, a mo ar proportion oftions a Group IVB metal salt and optionally about 10 parts of a diluentper part of metal salt. Visual inspection and, (B) PLATING W1 r H GROUPH B METALS where taken, the X-ray fluorescence or emission spectrumExamples to 71 of each resulting test piece showed a Group IV-B metallicMetal coupons to be plated, 1 in. x 1.5 in. x A in., Coatmg on ItsSurface were immersed in liquid plating compositions, consisting 50TABLE VII of 1 part of a bis(trialkylphosphine) metal halide dilutedwith about 2.5 parts of an inert solvent as specified in 3 salt RBRRSmvent 3 6?" 53E; the table below. The coupons were held in the bathsfor 75 T01 B t 1 N 100 C the times and at the temperatures noted in thetable be- 3 5 1 SQZHgfiffdffi": 40 E8 77 ..I"C1 -.d A t 't '1 100 Dlstgvtergmoved, rinsed wlth water and acetone, and 1n 5 78 i g g fi g m0i g f 91ml 6. S ee Yellow metal substrates were chosen for these tests79 TiIB Dir l l et yleli aethylghos- 100 Copper. so that the formationof silvery-white metal coatings 80 Zrch g gif; would be readily apparenton visual inspection. All coat- 81 Zr012 gg g y y ormam- 100 Do. ingswere adherent.

TABLE VI Example Plating Composition Tergll, Tfime, Substrate Result 65[(OH P] -ZnBr +dimethyl- 100 0.5 Copper.-- Zn coating.

iormamide. 66 [(C4H )3P]2-Zu(OC(O)CH3)2 25 24 Brass Do.

plus dimethyltormamide. 67 [((CH3)2N)3P]2-ZI1Clzp1llS 100 24 Copper.--Heavy Zn hexamethylphosphoramide. coatmg. 68 [((CHa)2N)aP]2-ZI1I2 plus100 24 d0 Do.

hexamethylphosphoramide. 69 [(C4H9)3P]2-Cd0lz plus 0.5 .do Lustroustetradecane. 3

plating.

11 (E) PLATING WITH GROUP v METALS Examples 82 to 88- Metal plates wereproduced on copper test coupons with the plating compositions specifiedin the table below which were prepared as in Examples 75 to 81. Heatingwas 16 hours at 100 C. except in the case of Example 88 which was for 12hours. Plating in Examples 82 to 84 was confirmed by X-ray emission andfluorescence spectra of the coatings.

(F) PLATING WITH GROUP VI METALS Examples 89 to '92 Metal plates wereproduced on copper test coupons with the plating compositions specifiedin the table below which were prepared as in Examples 75 to 81. Heatingwas 16 hours at 100 C. X-ray emission spectroscopy confirmed that theExample 91 plate was chromium.

TABLE IX Plating Composition Salt Pliosphine, R3P,R= Solvent CrClaDimethylamino Dimethyltormamide. CrCla d Do. CrClz do Do. 92 MoCla doNone.

(G) PLATING WITH GROUP VII METAL Example 93 Following the procedure ofExamples 75 to 81, a manganese coating, confirmed by X-ray emissionspectroscopy, was plated on copper by heating a test coupon in a [(CHP-MnCl hexamethylphosphoramide solution for 12 hours at 150 C.

(H) PLATING WITH GROUP VIII METALS Examples 94 to 103 The procedurefollowed was essentially that described for Examples 75 to 81, exceptthat the plating compositions and conditions were varied as noted in thetable below. In Example 94 the coating was confirmed by emissionspectroscopy. In Examples 94 to 97, the salt and phosphine wereseparately added to the solvent; in Examples 98 to 103, the preformedcomplex MX -R P was added directly to the plating solvent. In all casesthe coatings were adherent.

12 Example 104 About 1 g. of finely powdered [(CH P] -PdCl was spread ona 2 ml thick, 3 in. x 3 in. square of a high temperature resistantKapton type H polyimide film. The coated film was gradually heated on ahot plate under a nitrogen atmosphere to about 350 C. until the complexhad decomposed and had deposited on the film an adherent, lustrous,electrically-conductive palladium coating.

Such metallized polyimide structures are particularly useful forpreparing mirrors, automotive interior hardware, printed circuits andbattery electrodes.

(I) EXAMPLES I'LLUSTRATING IMPROVEMENTS WITHIN THE SCOPE OF THISINVENTION Example 105 One part of (CH P-AuCl was dissolved in 25 partsof a 15% solution of Orlon polyacrylonitrile in dimethylformamide. Thesolution was spread on a glass microscope slide and warmed with a heatlamp to evaporate the dimethylformamide. The slide was then exposed to aTesla coil spark discharge to sensitize the gold salt complex to thermaldecomposition and placed treated-side up on a 200 C. hot plate for about5 minutes. The resulting uniformly distributed golden coating wasadherent to the glass and electrically conductive.

Example 106 A (CH P -AuCl /polyacrylontrile/dimethylformamide solution,substantially as described in Example 105, was spread on a glass slideand the dimethylformamide evaporated by warming under a heat lamp. Theresulting film was then covered with a stencil, irradiated with highintensity light by contact flashing with a 200 watt-second xenon flashtube (Hico lite, Model K; one millisecond duration fiash), then heatedat C. for about 5 minutes. The resulting slide showed a lustrous,electrically conductive, adherent golden image corresponding to theirradiated areas.

Example 107 Example was repeated with 1 part of (CH3 3P per 5 parts ofpoly[4,4'(hexafluoroisopropylidene)diphenol isophthalate] polyester asthe carrier substrate in 100 parts of methylene chloride. The resultingfilm, after having been exposed to the spark discharge and heated at 200C. for 2 minutes, was golden, adherent and electrically conductive.

Such products are useful in printed circuitry for use at elevatedtemperatures.

Example 108 The procedure of Example 107 was repeated except that apiece of porcelain was used in place of the glass slide withsubstantially the same result.

TABLE X Plating Composition Example Temp., Time, Sub- Result SaltPhosphtne Solvent 0. hrs. strate R3P,R=

Me N Hexamethyl- 12 Copper.. Fe coat.

phosphoramide. Butyl Acetonitrile 80 3 d0 Co coat. R MezN Hexamethyl-150 12 do Rh coat.

phosphoramide. 97 NlBlg Phenyl 83% acetonitrlle, 17% 80 1 do Bright Niacetic acid. coat. 98 N101: Butyl Acetic acid 100 3. 5 d0 Lustrous Nicoat; 99 NiBn do .d0 100 2 Bronze. Do. 100.. NlClz 95% ethanol plus 5%70 2 Brass Ni coat.

cone. H01. do o 70 .1 do Lustrous Pd coat. 95% ethanol plus trace 70 7Copper Lustrous HF. Pt coat. do -do 70 7 ..do Pt coat.

13 Example 109 The procedure of Example 107 was repeated except that apiece of wood was used in place of the glass slide with substantiallythe same result.

Example 110 The procedure of Example 107 was repeated except that acarbon sheet was used in place of the glass slide with substantially thesame result.

Example 1 1 1 The procedure of Example 107 was repeated except that apiece of ceramic was used in place of the glass slide with substantiallythe same result.

Example 1 12 Repeating Example 107 with 0.5 part of the gold complexproduced uniformly colored purple slides, indicating colloidal golddispersed throughout the polymeric film, which were useful asinterference filters.

Example 1 13 A mixture of 1 part of (CH P-AgNO and 70 parts offilm-forming polyvinylchloride, cast as a film on glass fromdimethylformamide solution, was irradiated 3 times through a stencilwith the light source described in Example 1-06 and then heated to 180C. for 5 minutes to develop a silvery image. The silver deposit was muchless noticeable in the unirradiated area.

Example 114 The procedure of Example 113 was repeated except that 1 partof (C H P-AgClO was used as the silver complex with the same result.

Example 115 The procedure of Example 113 was repeated except that 1 partof (C H P-AgOC()CH was used as the silver complex with the same result.

Example 116 The procedure of Example 113 was repeated except that 1 partof (C H P-AgI was used as the silver complex with the same result.

Example 117 The procedure of Example 113 was repeated except that 1 partof (C H P-AgOC(O)CF was used as the silver complex with the same result.

Example 1 18 The procedure of Example 113 was repeated except that 1part of [(CgH P] -Ag CO' was used as the silver complex with the sameresult.

Example 119 The procedure of Example 113 was repeated except that 1 partof (C H P-AgCN was used as the silver complex with the same result.

Example 120 The procedure of Example 113 was repeated except that 1 partof (C H P-AgNO was used as the silver complex with the same result.

Example 121 metallized objects having continuous, adherent and, whereneeded, flexible, electrically conductive metal coatings. For example,it is useful to produce (1) metallic coatings that protect theunderlying material and that reflect light and infrared radiation; (2)electrically conductive articles such as printed circuits, resistors,capacitors, and electrodes for fuel cells and batteries; (3) variousdecorative pieces (e.g. automotive hardware); effects, and images basedon the formation of metal surfaces; (4) new catalyst structures whereina catalytically active heavy metal is impregnated and coated on a poroussubstrate carrier; and (5) metallized films showing selective lighttransmission which can be used as optical filters. It is also useful toobtain coatings of the normally brittle metals such as titanium,zirconium, chromium, vanadium, niobium, and manganese which aredifiicult to obtain by other methods. It is also useful to producemetallized plastics wherein the metal is uniformly distributedthroughout the body of the plastic as well as on its surface. This is ofgreat practical advantage when the surface of the plastic is normallysubjected to abrasion.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A method of chemically metalizing a substrate which comprises heatinga metal salt/phosphjne complex derived from one mole of anon-organometallic salt of a normally solid heavy metal of the DemingPeriodic Table and 1 .to 4 moles of a triorganophosph ine in which eachorgano group is a hydrocarbyl or dihydrocarbylamino radical in thepresence of the substrate to be metallized at a temperature of 25 to 350C., but below the decomposition temperature of the substrate and themetal salt alone, provided that when the substrate is not a heavy metalof the Deming Periodic Table other than the plating metal, the metalsalt/phosphine complex is in substantially pure form in direct contactwith the substrate.

2. The method of claim 1 in which the substrate is a heavy metal otherthan the plating metal, the metal salt/ phosph-ine complex is dissolvedin an inert solvent and the temperature is 25 to 150 C.

3. The method of claim 2 in which the complex is derived from a salt ofa heavy metal of Group I-B or VIII of the Deming Periodic Table and atrialkylphosphine.

4. The method of claim 1 in which the substrate is not a heavy metalother than the plating metal.

5. The method of claim 4 in which a solution containing the metalsalt/phosphi-ne complex in a volatile inert solvent is coated on thesubstrate, the solvent is evaporated, and the coated substrate is heatedto metallize the surface.

6. The method of claim 5 in which the complex is derived from a salt ofa heavy metal of Group I-B or VIIII of the Deming Periodic Table and atrialkylphosp me.

7. The method of claim 5 in which the temperature is to 350 C.

8. The method of claim 6 in which the complex is derived from goldchloride and a tri-lower alkylphosphine and the substrate is a polymericmaterial.

9. The method of claim 6 in which the complex is derived from silvernitrite 'and a tri-lower alkylphosphine and the substrate is a polymericmaterial.

10. The method of claim 6 in which the complex is derived from silvernitrite and a tri-lower alkylphosphine and the substrate is a porousceramic body.

11. The method of claim 6 in which the complex is derived from palladiumchloride and a tri-lower alkylphosphine and the substrate is a polymericmaterial.

12. The method of claim 4 in which the met-a1 salt/ phosphine complexand a soluble polymer are dissolved in a mutual inert volatile solvent,the solvent is evaporated to form an intimate salt/phosphine/polymermix- 15 ture, and the mixture is heated to produce a metallizedpolymeric product.

13. The method of claim 12 in which the complex is derived from a saltof a heavy metal of Group I-B or VIII of the Deming Periodic Table and atrialkylphosphine.

14. The method of claim 13 in which the temperature is 100 to 350 C.

15. The method of claim 13 in which the complex is derived from goldchloride and a tri-lower alkylphosphine.

16. The method of claim 13 in which the complex is derived from silvernitrite and a tri-lower alkylphosphine.

1 6 References Cited UNITED STATES PATENTS 3,013,039 12/1961 Lambert eta1. 260-429 3,054,815 9/1962 Schroll 260439 5 3,294,828 12/1966 Werner117-l07.2 X 3,320,293 5/1967 Colfey ll7130 X OTHER REFERENCES Mukaiyamaet al., Jour. of Org. Chem, vol. 28, p. 917, 10 April 1963.

RALPH S. KENDALL, Primary Examiner.

. US. Cl. X.R.

1. A METHOD OF CHEMICALLY METALIZING A SUBSTRATE WHICH COMPRISES HEATINGA METAL SALT/PHOSPHINE COMPLEX DERIVED FROM ONE MOLE OF ANON-ORGANOMETALLIC SALT OF A NORMALLY SOLID HEAVY METAL OF THE DEMINGPERIODIC TABLE AND 1 TO 4 MOLES OF A TRIOGANOPHOSPHINE IN WHICH EACHORGANO GROUP IS A HYDROCARBYL OR DIHYDROCARBYLAMINO RADICAL IN THEPRESENCE OF THE SUBSTATE TO BE METALLIZED AT A TEMPERATURE OF 25* TO350*C., BUT BELOW THE DECOMPOSITION TEMPERATURE OF THE SUBSTRATE AND THEMETAL SALT ALONE, PROVIDED THAT WHEN THE SUBSTRATE IS NOT A HEAVY METALOF THE DEMING PERIODIC TABLE OTHER THAN THE PLATING METAL, THE METALSALT/PHOSPHINE COMPLEX IS IN SUBSTANTIALLY PURE FORM IN DIRECT CONTACTWITH THE SUBSTRATE.